Friendships

So I have this friend and we always seem to get really close then she finds someone new and ditches me for a while then comeback says sorry and expect everything to go back to normal. She had done this to me a lot and It really hurts to know that I’m always second choice. She has also done it with some other people in my group and she has made up with all of them but not with me. I keep trying to talk to her but she keeps acting like in invisible and ignores me. I’m done getting hurt by her and then forgiving her just for her to do it all again but I also don’t want to lose any of my other friends in my group and if I don’t forgive her I feel like the whole group is going to turn on me and leave me out and blame me for not forgiving her. I honestly don’t want to be her friend any more because she had never been a good friend to me but I don’t want to lose my other friends because of her what should I do?